Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$78.81	13.529%	$89.4722	$89.47	$89.45	$89.50
Purchase #2	$58.39	11.108%	$64.876	$64.88	$64.90	$64.90
Purchase #3	$229.53	7.659%	$247.1097	$247.11	$247.10	$247.10
Purchase #4	$124.58	3.472%	$128.9054	$128.91	$128.90	$128.90
Purchase #5	$175.28	3.851%	$182.03	$182.03	$182.05	$182.00
Purchase #6	$170.87	7.522%	$183.7228	$183.72	$183.70	$183.70
Purchase #7	$180.34	10.671%	$199.5841	$199.58	$199.60	$199.60
7 purchase totals =	$1,017.80		$1,095.7002	$1,095.70	$1,095.70	$1,095.70